The present invention relates to spinal implants and methods of implantation and use of the implants in general, and more particularly to spinal implants for replacing at least the spinous process and/or for operating as cross-links and methods relating to same.
Referring to FIG. 1 a perspective view of the spinal anatomy is shown. Briefly, the spinal column 100 is divided into five sections beginning with the cervical section 102, the thoracic section 104, the lumbar section 106, the sacrum 108 and finally the coccyx 110. Each major section (cervical 102, thoracic 104, lumbar 106) is made up of individual bones called vertebrae. In a conventional spinal configuration, there are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae.
An individual vertebra is made up of several anatomical features. Generally, each vertebra of the three major sections has the same major features. FIG. 2 is a cross-sectional view of a thoracic vertebra 200. The body 202 of the vertebra is the primary area of weight bearing and provides a resting place for the fibrous discs which separate each of the vertebrae. The lamina 208 covers the spinal canal, the large opening in the center of the vertebra through which the spinal cord passes, and the neural foramen, where the spinal nerves exit. The spinous process 212 is the bone that can be felt when running a hand down a person's back. The paired transverse processes 204 are oriented 90 degrees to the spinous process 212 and provide attachment for back muscles. Pedicles 206 connect the transverse processes 204 to the body 202. Located between the transverse processes 204 and the laminae 208 are superior articular processes 210.
Often times, one or some of the major vertebral features is removed to effectuate treatment of a patient, for example in a laminectomy at least a portion of a lamina 208 is removed. It is not unusual for some or all of the spinous process 212, the laminae 208, the superior articular processes 210 or even the transverse processes 204 to be removed in a surgical procedure.
U.S. Pat. Nos. 7,566,345, 6,902,580 and 6,419,703 to Fallin, et al., the disclosures of which are incorporated herein by reference, describe prosthetic replacements for a posterior element of a vertebra comprising portions that replace the natural lamina and the four natural facets. The prosthetic replacements may also include portions that replace one or more of the natural spinous process and the two natural transverse processes. If desired, the prosthesis replacements may also replace the natural pedicles. Methods for replacing a posterior element of a vertebra are also provided.
United States Patent Application Publication No. US 2005/0033434 to Berry, the disclosure of which is incorporated herein by reference, describes a prosthetic device for interposition in a space left by one or more excised vertebral posterior structures. The prosthetic device comprises a lamina bridge having an inferior portion for replacing an excised lamina; at least one inferior facet replacement device, connected to the inferior portion of the lamina bridge, to replace an excised inferior articular process; and at least one superior facet replacement device to replace an excised superior articular process. The at least one superior facet replacement device articulates with the at least one inferior facet replacement device.
United States Patent Application Publication No. US 2005/0010291 to Stinson, et al., the disclosure of which is incorporated herein by reference, describes cephalad and caudal vertebral facet joint prostheses and methods of use. The cephalad prostheses are adapted and configured to be attached to a lamina portion of a vertebra without blocking a pedicle portion of the cephalad vertebra. In some embodiments, the prosthesis is attached with a non-invasive support member, such as a clamp. In other embodiments, a translaminar screw may be used for additional fixation.
PCT Application Publication No. WO 99/23963 to Senegas, the disclosure of which is incorporated herein by reference, describes a cervical vertebra implant comprising two branches adapted to extend respectively substantially along two cervical blades of a common cervical vertebra spaced from each other after osteotomy of the blades, and a rigid body linking the two branches.